KASAN report a uaf when recover intents fails:
==================================================================
BUG: KASAN: slab-use-after-free in xfs_cui_release+0xb7/0xc0
Read of size 4 at addr ffff888012575e60 by task kworker/u8:3/103
CPU: 3 PID: 103 Comm: kworker/u8:3 Not tainted 6.4.0-rc7-next-20230619-00003-g94543a53f9a4-dirty #166
Workqueue: xfs-cil/sda xlog_cil_push_work
Call Trace:
<TASK>
dump_stack_lvl+0x50/0x70
print_report+0xc2/0x600
kasan_report+0xb6/0xe0
xfs_cui_release+0xb7/0xc0
xfs_cud_item_release+0x3c/0x90
xfs_trans_committed_bulk+0x2d5/0x7f0
xlog_cil_committed+0xaba/0xf20
xlog_cil_push_work+0x1a60/0x2360
process_one_work+0x78e/0x1140
worker_thread+0x58b/0xf60
kthread+0x2cd/0x3c0
ret_from_fork+0x1f/0x30
</TASK>
Allocated by task 531:
kasan_save_stack+0x22/0x40
kasan_set_track+0x25/0x30
__kasan_slab_alloc+0x55/0x60
kmem_cache_alloc+0x195/0x5f0
xfs_cui_init+0x198/0x1d0
xlog_recover_cui_commit_pass2+0x133/0x5f0
xlog_recover_items_pass2+0x107/0x230
xlog_recover_commit_trans+0x3e7/0x9c0
xlog_recovery_process_trans+0x140/0x1d0
xlog_recover_process_ophdr+0x1a0/0x3d0
xlog_recover_process_data+0x108/0x2d0
xlog_recover_process+0x1f6/0x280
xlog_do_recovery_pass+0x609/0xdb0
xlog_do_log_recovery+0x84/0xe0
xlog_do_recover+0x7d/0x470
xlog_recover+0x25f/0x490
xfs_log_mount+0x2dd/0x6f0
xfs_mountfs+0x11ce/0x1e70
xfs_fs_fill_super+0x10ec/0x1b20
get_tree_bdev+0x3c8/0x730
vfs_get_tree+0x89/0x2c0
path_mount+0xecf/0x1800
do_mount+0xf3/0x110
__x64_sys_mount+0x154/0x1f0
do_syscall_64+0x39/0x80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
Freed by task 531:
kasan_save_stack+0x22/0x40
kasan_set_track+0x25/0x30
kasan_save_free_info+0x2b/0x40
__kasan_slab_free+0x114/0x1b0
kmem_cache_free+0xf8/0x510
xfs_cui_item_free+0x95/0xb0
xfs_cui_release+0x86/0xc0
xlog_recover_cancel_intents.isra.0+0xf8/0x210
xlog_recover_finish+0x7e7/0x980
xfs_log_mount_finish+0x2bb/0x4a0
xfs_mountfs+0x14bf/0x1e70
xfs_fs_fill_super+0x10ec/0x1b20
get_tree_bdev+0x3c8/0x730
vfs_get_tree+0x89/0x2c0
path_mount+0xecf/0x1800
do_mount+0xf3/0x110
__x64_sys_mount+0x154/0x1f0
do_syscall_64+0x39/0x80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
The buggy address belongs to the object at ffff888012575dc8
which belongs to the cache xfs_cui_item of size 432
The buggy address is located 152 bytes inside of
freed 432-byte region [ffff888012575dc8, ffff888012575f78)
The buggy address belongs to the physical page:
page:ffffea0000495d00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888012576208 pfn:0x12574
head:ffffea0000495d00 order:2 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x1fffff80010200(slab|head|node=0|zone=1|lastcpupid=0x1fffff)
page_type: 0xffffffff()
raw: 001fffff80010200 ffff888012092f40 ffff888014570150 ffff888014570150
raw: ffff888012576208 00000000001e0010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff888012575d00: fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc
ffff888012575d80: fc fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb
>ffff888012575e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888012575e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888012575f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
==================================================================
If process intents fails, intent items left in AIL will be delete
from AIL and freed in error handling, even intent items that have been
recovered and created done items. After this, uaf will be triggered when
done item commited, because at this point the released intent item will
be accessed.
xlog_recover_finish xlog_cil_push_work
---------------------------- ---------------------------
xlog_recover_process_intents
xfs_cui_item_recover//cui_refcount == 1
xfs_trans_get_cud
xfs_trans_commit
<add cud item to cil>
xfs_cui_item_recover
<error occurred and return>
xlog_recover_cancel_intents
xfs_cui_release //cui_refcount == 0
xfs_cui_item_free //free cui
<release other intent items>
xlog_force_shutdown //shutdown
<...>
<push items in cil>
xlog_cil_committed
xfs_cud_item_release
xfs_cui_release // UAF
Fix it by move log force forward to make sure done items committed before
cancel intents.
Fixes: 2e76f188fd90 ("xfs: cancel intents immediately if process_intents fails")
Signed-off-by: Long Li <leo.lilong@xxxxxxxxxx>
---
fs/xfs/xfs_log_recover.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index fdaa0ffe029b..c37031e64db5 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -3444,6 +3444,13 @@ xlog_recover_finish(
int error;
error = xlog_recover_process_intents(log);
+ /*
+ * Sync the log to get all the intents that have done item out of
+ * the AIL. This isn't absolutely necessary, but it helps in case
+ * the unlink transactions would have problems pushing the intents
+ * out of the way.
+ */
+ xfs_log_force(log->l_mp, XFS_LOG_SYNC);
if (error) {
/*
* Cancel all the unprocessed intent items now so that we don't
@@ -3458,13 +3465,6 @@ xlog_recover_finish(
return error;
}
- /*
- * Sync the log to get all the intents out of the AIL. This isn't
- * absolutely necessary, but it helps in case the unlink transactions
- * would have problems pushing the intents out of the way.
- */
- xfs_log_force(log->l_mp, XFS_LOG_SYNC);
-
/*
* Now that we've recovered the log and all the intents, we can clear
* the log incompat feature bits in the superblock because there's no
--
2.31.1
